Current situation and perspectives

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• Circumstances, nature and main origins of the accidents studied p. 45 - Accident circumstances p. 45 - Failures observed p. 46 - Origin of the accidents p. 47 - Quantities of ammonia released p. 48 . Refrigerating installations p. 49 . Other installations (miscellaneous activities) p. 49 Case study of typical refrigeration accident p. 51

• Accident of 12/02/94 (HOCHFELDEN - Bas Rhin) p. 51

• Accident of 11/21/94 (CONNERRE - Sarthe) p. 52

• Accident of 08/11/94 (REIMS - Marne) p. 53

• Accident of 06/13/94 (NANTERRE - Hauts de Sienne) p. 54

• Accident of 03/11/94 (SAINT BRANDAN - Côtes d'Amor) p. 55

• Accident of 02/17/94 (DUCEY - Manche) p. 56

• Accident of 05/17/93 (GUERLESQUIN - Finistère) p. 59

• Accident of 06/17/92 (SECLIN - Nord) p. 60

• Accident of 07/18/91 (LANDERNEAU - Finistère) p. 62

• Accident of 10/11/90 (MONTELIMAR - Drome) p. 63

• Accident of 10/08/90 (DIEUE-SUR-MEUSE - Meuse) p. 65

• Accident of 10/03/90 (MONDEVILLE - Calvados) p. 66

• Accident of 08/01/90 (MONTELIMAR - Drome) p. 67

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Summary of the information gathered - Bibliographic study

Risks p. 69

• Fire / explosion risk p. 73

Consequences p. 75 Evolution perspectives p. 75

Conclusions - Recommendations

Installation design, construction and commissioning p. 78

• Fire risk p. 81

Operation, repair and inspections p. 82 Training of contractors p. 84 Intervention / Evacuation p. 85

Appendices

Appendix 1: type and characteristics of industrial refrigeration systems.

Appendix 2: current technologies and alternatives.

Appendix 3: physical and thermodynamic characteristics of ammonia.

Appendix 4: toxicological sheet.

Appendix 5: distribution of activities in France (1992 INSEE statistical extracts).

Appendix 6: texts and standards applicable to refrigeration systems.

Appendix 7: list of known accidents since 1958 (France / World).

Appendix 8: fault trees.

References

Bibliography Useful addresses

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GLOSSARY

LP Low Pressure.

C.F.C. Chloro-Fluoro-Carbon.

G.W.P. Global Warming Potential. The GWP is a substance's earth warming potential by comparison with that of CO2. This value is strongly effected by the time period considered (20, 100, 500 years, etc.).

H.C.F.C. Hydro-Chloro-Fluoro-Carbon - Alternative transition fluid.

H.G.W.P. Halocarbon Global Warming Potential. A substance's greenhouse effect in relation to that of R11.

H.F.A. Hydro-Fluoro-Alcane (or FORANE equivalent to H.C.F.C. in France).

H.F.C. Hydro-Fluoro-Carbon - The alternate fluid of the future, containing no chlorine (O.D.P. = 0) although does have a greenhouse effect.

HP High Pressure.

O.D.P. Ozone Depletion Potential (index characterising a molecule's participation in the destruction of the ozone layer).

R11 C.F.C. - Trichlorofluoromethane (CCl3F).

R113 C.F.C. - Trichlorofluoroethane (CCl2F-CClF2).

R114 C.F.C. - Dichlorotetrafluoroethane (CClF2-CClF2).

R115 C.F.C. - Monochloropentafluoroethane (CClF2-CF3).

R12 C.F.C. - Dichlorodifluoromethane (CCl2F2).

R13 C.F.C. - Monochlorotrifluoromethane (CClF3).

R13B1 C.F.C. - Trifluorobromomethane (CF3Br).

R134a H.F.C. - (1st alternate fluid for R12).

R152a H.F.C. - Difluoroethane (CH3-CHF2).

R22 H.C.F.C. - Monochlorodifluoromethane (CHClF2).

R23 H.C.F.C. - Trifluoromethane (CHF3).

R404A H.F.C. - (substitute for R502).

R500 C.F.C. - Azeotropic mixture (73.8% R12 and 26.2% R152a).

R502 C.F.C. - Azeotropic mixture (48.8% R22 and 51.2% R115).

R503 C.F.C. - Azeotropic mixture (59.9% R13 and 40.1% R23).

R717 Anhydrous ammonia ("refrigerant quality", 99.95% minimum purity).

T.E.W.I. Total Equivalent Warning Impact (index characterising the refrigeration system's impact on the greenhouse effect).

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INTRODUCTION

History

The first practical refrigeration machine appeared in the middle of the last century following a patent filed by Jacob Perkins in 1834 concerning a vapour compression system¹.

Cold was produced artificially for the first time in 1857. At the Universal Exposition in London, Ferdinand Carre presented an absorption-type machine which made ice cubes almost continuously. The machine used ammonia as a refrigerant and water as the absorption substance. In 1874, Pictet built the first compression machine. His machine used sulphur dioxide (SO2), while Lowe, in the United States, manufactured comparable machines that operated on carbon dioxide (CO2).

Ammonia was used for the first time in a vapour compression machine built by Carl Von Linde in 1876. Following the Paris Universal Exposition of 1878, the majority of large breweries began using ammonia compression systems. In 1876, a Frenchman by the name of Charles Tellier equipped a 650-ton ship (the "Frigorifique") to transport a cargo of frozen meet to Buenos Aires in 3 months and in excellent condition². Quick- freezing, as it is practiced today, was invented in 1929 by an American, Clarence Birdseye, who filed a patent concerning quick-freezing of perishable foodstuffs.

Numerous refrigerants were used such as dimethyl ether, which is explosive and was rapidly replaced by ammonia, carbon dioxide, sulphur dioxide, propane and methyl chloride (CH3Cl)³. In the early 20th century, the need for refrigeration increased. This development was associated with a growth in agricultural production and a new activity sectors which called upon refrigeration techniques (the dairy, meat processing industries, and the maritime transport of perishable foodstuffs). The competition between the various refrigerants increased.

1 L'ammoniac utilisé comme frigorigène, Ammonia used as coolant (INTERNATIONAL INSTITUTE OF REFRIGERATION I.I.R. - 1993).

2 Petit livre bleu des surgelés des glaces, Small blue book of quick-frozen foods, ice cream (Ficur - 1987).

3 La sécurité et l'ammoniac, Safety and ammonia (Magazine Générale du Froid, No. 74 / G. VRINAT - June 1990).

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The uses of ammonia and carbon dioxide varied according to the country, although in the 1920's, ammonia progressively took precedence in large industrial installations and on board ships. Low power installations use sulphur dioxide and methyl chloride in particular.

It wasn't until the 1930's and the development of domestic refrigeration that the American company, Kinetic Chemicals, developed chloro-fluoro-carbon (C.F.C.) synthetic fluids whose high molecular mass is well suited to centrifugal compression and allowed the development of hermetic compressors^3/⁴. C.F.C.s then progressively replaced methyl chloride, CO2 and SO2. The main C.F.C.s are essentially⁵:

• R12 (CF2Cl2) for applications in the vicinity of 0°C and especially the air- conditioning of occupational settings, industrial heat pumps, and the refrigeration and storage of fresh foodstuffs,

• R11 (CFCl3) used in centrifugal machines,

• R502 (a mixture of R22 / CHClF2 and R115) for low temperatures such as freezing and the storage of frozen foods and ice cream products. This refrigerant is also used in "frozen food display cases" in supermarkets and hypermarkets.

Current situation and perspectives

In 1974, the American chemist, F. Sherwood Rowland, postulated a significant destruction of the ozone layer in the upper atmosphere by the chlorine contained in C.F.C.s. In the autumn of 1987, a "hole" was detected in the ozone layer above Antarctica. This anomaly is attributed, at least partly, to C.F.C.s. The international community decided to limit their production and to prohibit them once and for all as of January 1st, 1996 (the Vienna Convention in 1985, the Montreal Protocol in September 1987, the London Agreement in 1990 and the Copenhagen conference in 1992).

Excluding new materials and techniques, this common position of the governments had two consequences:

• for the upcoming years, the main producers of C.F.C. propose substitute refrigerants such as hydro-chloro-fluroro-carbon compounds (H.C.F.C.) or hydro-fluoro-alcanes (H.F.A. or FORANE, in France), less aggressive transition fluids, and are searching for new totally neutral molecules in the long term,

4 Production du froid - Technologie des machines industrielles, Cold production - Technology of industrial machines

(Les Technologies de l'Ingénieur / Georges VRINAT).

5 SAVE summer training program - Club M3E (Association Française du Froid /A.F.F. G. VRINAT - 1994).

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The main H.C.F.C. is R22, which is widely used in industrial type food freezing and storage installations,

• the return of old refrigeration fluids and essentially ammonia...

Ammonia can be used in the majority of industrial refrigeration, freezing installations and stores at all temperatures.

Refrigerants have a double effect on the environment^5/⁶:

• effect on life forms characterised by the O.D.P. (ozone depletion potential),

• effect on the climate characterised by the H.G.W.P. (hydrocarbon global warming potential) and the T.E.W.I. (impact with relation to CO2).

Refrigerant Ozone ODP/R11

Greenhouse effect

HWP

TEWI/CO2 20 year

period

period R12 0.9 to 1 2.8 to 3.4 7,100 7,300 4,500 R502 0.17 to 0.28 4.02 4,820 4,260 4,040 R22 0.04 to 0.06 0.32 to 0.37 4,100 1,500 510

R717 (NH3) 0 0 0 0 0

Nowadays, industry uses refrigeration to a wide extent, to liquefy gases, condense volatile liquids, crystallise salts, control violent reactions or more simply... to preserve sensitive products from "heat" and perishable foodstuffs.

The economic impact of refrigeration techniques throughout the world is extensive⁷^/⁸. The overall amount of yearly investments in refrigeration equipment is nearly 500 billion French francs, the value of the products preserved by cold would represent 10 times that amount. There is approximately 300 millions metric cubes of refrigerated storage capacity in the world, allowing to store 5% of the total annual product of foodstuffs at any given time. Considering retail trade, refrigerated transports and domestic appliances, 10 to 25% of the world's food production enters the "cold chain" at one stage or another.

Used for decades owing to its excellent thermodynamic properties and progressively replaced over the last twenty years, particularly by C.F.C.s (not thermally efficient

6 Total Equivalent Warming Impact (T.E.W.I.) M. DUMINIL (Magazine Générale du Froid, No. 36 - October 1993).

7 Ammonia used as coolant (INTERNATIONAL INSTITUTE OF REFRIGERATION I.I.R. / I.I.R - 1993).

8 The CFC/Ozone problem and possibilities for emission reduction in Refrigeration, Air Conditioning and Heat Pump applications (DKV / Statusberich No. 2 - July 1987).

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although non-toxic), ammonia is returning to the forefront as a calorific fluid little by little. In 1984, the world production of ammonia was 120 million tons; less than 5% of this production was used as a refrigerant under the code R717 (at least 99.95% pure).

Ammonia refrigeration units can be used in refrigerated storage or in certain sport complexes (ice skating rinks, etc.), for example. By their nature, these activities are often located in or near the urban fabric. An often-sensitive environment, the facility including the units concerned and the redevelopment of the use of ammonia as a potential substitute for C.F.C.s fully justifies this research study⁹.

9 Appendices 1 and 2: Type and characteristics of industrial refrigeration installations / Current and alternative technologies.

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LIQUEFIED AMMONIA

REFRIGERATING INSTALLATIONS

Cold production

General

Cold is produced by absorbing heat to a temperature below that of the ambient environment. The numerous processes used are habitually classified according to the type of basic phenomena that they use. We can thus distinguish ¹⁰:

• the thermodynamic methods, which use endothermic phenomena accompanying the phase changes (fusion, sublimation, evaporation, expansion or dissolution) or certain chemical reactions,

• the electrical or magnetic processes, which slow down molecular agitation at the origin of the heat phenomena by subjecting refrigerant atoms to an electric current or a magnetic field.

Thermodynamic methods are the most popular. Cold is most often produced by the expansion of a compressed gas, generally of the FORANE (or FREON) family or by evaporation of a fluid with a low vapour tension, such as ammonia. The vast majority of systems using these methods implement a compression and expansion cycle, in a closed circuit, in which the fluid conveyed, essentially gaseous, may or may not undergo a phase change.

As the transfer of heat occurs spontaneously toward lower temperatures, the intermediate fluid is used after first lowering its temperature. It is thus referred to as a refrigerant.

10 12 technologies pour l'avenir de l'environnement, 12 technologies for the future of the environment (French Ministry of Industry and External Commerce / SRI International - 1992).

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Theoretical refrigeration cycle

In order to absorb heat at low temperature (the useful part of the cycle!), the majority of processes that implement an intermediate fluid flow in a closed cycle to reproduce the refrigeration development of the entire system as many times as necessary.

Technical refrigeration is essentially produced by vapour compression systems. A vapour compression cycle features the following main elements:

• an evaporator, in which vaporisation of the refrigerant removes a quantity of heat Q0 to the outside environment,

• a mechanical compressor that draws in the vapours formed in the evaporator at pressure P₂ to compress and expel them at pressure P₁. The compressor absorbs mechanical energy W,

• a condenser, in which the refrigerant condenses and releases a certain quantity of heat Q into the outside environment,

• a fixed expansion valve, through which the refrigerant flows to return to the evaporator, its pressure being brought from P1 to P2.

Refrigerating cycle flow diagram

A theoretical refrigeration cycle includes the following 4 phases:

• vaporisation of a fluid at constant pressure and temperature (P2 & T2), with absorption of a quantity of evaporated fluid heat (Q0 / kg), borrowed from the outside environment of temperature T2' > T2 (cold production),

• adiabatic compression (without heat flow) of the humid vapour in a compressor which brings the pressure to the value P1, and vapour tension of

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the fluid to condensing temperature T1. This compression absorbs a certain amount of work supplied by an external energy source,

• condensation of the fluid in the condenser, at pressure P1 and temperature T1, depending on the unit and the temperature T1' of the external environment where the condensation heat Q1 will flow (with naturally T1 >

T1'),

• adiabatic expansion of the refrigerant in an expansion valve attached to the same shaft as the compressor to recover this expansion work of the pressure P1 of the condenser to that of the evaporator P2.

In order to translate these phenomena, the refrigeration industry often uses:

• either an enthalpy/pressure (H, P) diagram. The values used in the calculations, characterising the fluid state, are thus the pressure (P), the absolute temperature (T), the enthalpy (H), the specific volume (V), the titer (x) and the entropy (S),

• or an entropy diagram (S, T) in which a CARNOT ABCD cycle evolving between 2 isotherms (T1 & T2) and 2 adiabatics (AD and BC) represents the operation. The curves delineate different areas which correspond to the heat exhausted to the condenser (Q1), to that absorbed by the evaporator (Q2), to the work absorbed by the compressor, to that recovered in the expansion valve and to that consumed by the machine. A coefficient of performance (T2/(T1-T2)) can then be calculated.

Actual refrigeration cycle

The actual refrigeration cycle of a machine can differ from the theoretical cycle depending on, for example, the various equipment installed on the installation (motor energy savers, etc.).

Compression refrigeration systems using ammonia as refrigerant

The design of refrigeration machines using ammonia or halogenated fluids is comparable. The components, however, are made of ordinary steel, as copper, copper alloys and zinc are attacked by ammonia. Considering its intrinsic characteristics and particularly its incompatibility with cupreous metals but also the market share that it currently represents, equipment adapted to ammonia is very specific and less widespread than its "halogenated fluid" type counterpart¹¹.

Finally, the intensive turn to halogenated fluids in all fields using refrigeration has resulted in the development of techniques that are more advanced than those required by

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ammonia and simpler installation practices. Ultimately, the practices, inevitably more strict used for ammonia systems, are sometimes not or little known by installers ¹². A natural substance, ammonia is also synthesised in large quantities by the chemical industry. As a refrigerant, it has certain advantages and, in particular:

• good thermodynamic properties (heat/mass transfer) enabling machines with one of the best performance coefficients existing to be obtained. The mass over installed power ratio is in the order of 5.5 kg of NH3/kW¹³,

• a higher critical temperature,

• a higher vaporisation enthalpy, making it possible to produce temperatures as low as - 60°C,

• chemical neutrality vis-à-vis components of the refrigeration system, excluding copper and its alloys as well as reliability in the presence of humid air and water,

• better stability vis-à-vis oil,

• easy leak detection, even small leaks (olfactory detection at 5 ppm, etc.),

• it has no atmospheric ozone effect or greenhouse effect contribution,

• the lowest purchase price of all refrigerants (5 to 8 times cheaper per kg, 11 to 17 times when the reduction in installation size is taken into account),

• reduced pumping cost for embedded systems and reduced piping dimensions for the same refrigerating power,

In relation to the other refrigerants and at equal energy efficiency, a lower mass flow (proportional to the mole weight of the fluid), piston speed from 2.5 to 3.2 times greater ¹⁴ (inversely proportional to the square root of this weight), as well as greater heat transfer at the evaporation/condensation stages (linked to the lightness of ammonia) and finally, better thermal conductivity (point 1 above), all lead to lower production costs for an installation¹⁵.

The restrictions associated with its use are due to the related hazards, and in particular:

• a potential character as an flammable gas,

• the strong exothermicity of its dissolution in water,

• its toxicity at low concentrations in air (25 ppm),

12 La sécurité et l'ammoniac, Safety and ammonia (Magazine Générale du Froid, No. 74 / G. VRINAT - June 1990).

13 Guide d'étude des risques technologiques, Technological risks study guide (AFF / Club Ammoniac - 1995).

14 This characteristic, which has not yet been exploited industrially, may enable a significant reduction in the size and cost of compressors.

15 L'ammoniac utilisé comme frigorigène, Ammonia used as coolant (INTERNATIONAL INSTITUTE OF REFRIGERATION I.I.R. / I.I.R - 1993).

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• the relatively high pressures that it needs requiring steel thicknesses greater than those of compounds used with halogenated refrigerants.

Ammonia's ignition hazard and toxicity are dealt with in greater detail in the following paragraphs.

Implementation of ammonia¹¹

Ammonia differs in its implementation in relation to halogenated fluids in the following ways:

• the design of refrigeration systems is simpler (based on the unique general behaviour of ammonia). The use of each of the halogenated fluids and their azeotropic mixtures requires complete specific knowledge of the refrigerant associated with lubrication oil problems (zero, total or partial miscibility), transport properties, and thermal exchange coefficients, etc... ,

Furthermore, with this design, the size of return lines does not pose a problem for solving oil return problems. Only the return of liquid to the compressor must be avoided.

• the operation of an ammonia-based system can be more complicated.

Ammonia systems require a set of different components and often more difficult to procure than those used for halogenated fluids,

• welders must have specific skills associated with steel pipe technology and their assembly (approved by the Institut de Soudure as per standard NF A 88-110, etc.),

• circuits must be perfectly hermetic. These guidelines are less strict in the final preparation of the circuit. Considering the water solubility of ammonia, there is no need to apply a high vacuum to the circuits prior to filling,

• for the same internal circuit volume and identical fill factor, the mass of ammonia is 2 times lower than that of halogenated fluids,

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• the installations must be permanently monitored by alarm systems (explosimeters). When a leak occurs and for a given threshold, an air extraction system must come on in the machine room and the operating personnel informed. A 2nd threshold must correspond to a general alarm and the disconnection of power to the electrical circuits in the machine room¹⁶.

The use of cold and installation typology

There are nearly 300,000 ammonia compression installations operating throughout the world ¹⁷, excluding household refrigerators and lost heat recovery industrial installations. Derived from well-controlled technology, ammonia has been used as a refrigerant for more than a century. These machines cover nearly all of our industrial or domestic needs in terms of medium or very large refrigeration capacity (greater than or equal to 100 kW of refrigeration).

Data relative to storage facilities in France¹⁸^/¹⁹

Type of store Number Capacity (m³) Public refrigeration storage facilities 293 5,604,193 Private refrigeration storage

facilities

4,984 9,456,470 Fruit packing houses 909 5,448,799

TOTAL 6,186(*) 20,509,462

(*) The profession indicates that 400 freezing companies representing 28,500 t/day of freezing are associated with some of these warehouses or cold storage facilities. More efficient for low temperatures (quick-freezing), ammonia is used in 36% of the sites although represents 55% of the installed power (S.E.I. / Profession meeting of July 27, 1993).

16 Détection de mélanges air/ammoniac à faible concentration / Recommandations, Detection of air/ammonia mixtures at low concentration / Recommendations (I.N.R.S. - 1992).

17 12 technologies pour l'avenir de l'environnement, 12 technologies for the future of the environment (Ministère de l'Industrie et du Commerce Extérieur / SRI International - 1992).

18 L'entreposage frigorifique français en chiffres, French cold storage in numbers - F. BILLARD and G.

PIERSON

(Magazine Générale du Froid, No. 50 - October 1992).

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Data relative to the quantities of refrigerant used

All French industries dealing with refrigeration would represent a stock of refrigerant of approximately 33,000 t²⁰; 27.5% of this capacity would be used in industries associated with human food, that is nearly 9,100 t made up of C.F.C. (R12, R502), H.C.F.C. (R22 mainly) and ammonia.

Type of activity Source CFC (t) HCFC (t) NH3 (t) Total (t) Public refrigeration storage facilities USNEF 60 400 540 1,000 Private refrigeration storage

facilities

Estimation 102 700 900 1,702 Fruit packing houses Estimation 60 400 500 960 Ice creams and ices FICUR 27 40 115 182 Quick-frozen product factories FICUR 11 70 210 291 Fresh dairy products EDF - 560 840 1,400

Beverages EDF 15 25 170 210

Meat processing EDF - 1,000 980 1,980 Vegetable processing EDF - 240 720 960

Baking industry EDF - 150 90 240

Grain processing EDF 100 10 75 185 Grand total (t) 375 3,595 5,140 9,110

Percentages 4 39.5 56.5 100

The table above shows that the C.F.C.s are used very little in the food industries, that H.C.F.C.s represent a large portion, to be replaced in the relatively near future, and that ammonia is already the most widely used refrigerant. A Dutch study ²¹ arrives at comparable results. The International Institute of Refrigeration also indicates that ammonia represents 59% of refrigerants (31% for the H.C.F.C.s with R22, 1% for the C.F.C.s with R12 and 9% with R502).

Of the 176 ice skating rinks in France, 91 are direct expansion type and 85 use a secondary refrigerant (glycol water or brine). C.F.C. 12 is used the most (400 t), while H.C.F.C. 12 represents 88 t and ammonia 43 t. In French ports, 170,000 t of ice is manufactured each year in the form of chips by direct expansion of ammonia. This activity sector represents 14 t of ammonia for the entire sector.

20 "Revue des applications électriques dans le résidentiel et le tertiaire", Review of electrical applications in the residential and tertiary sector, No. 35 - October 1993.

21 Ammonia as refrigerant. Applications and risks - R. J. M. VAN GERWEN (IIF B2 Hannover- May 1994).

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Installations can be classified according to various criteria such as evaporation temperature, ammonia distribution system, condensation mode, number of compressor stages and of course, according to the various applications²². This final classification is intentionally presented last using 7 different diagrams.

Classification according to evaporation temperatures

System Temperature (°C) Application T1 - Low temperature - 40 to - 45 Quick freezing T2 - Medium temperature - 25 to - 30 Frozen food storage T3 - High temperature - 10 to 0 Refrigeration T4 - Very high temperature T0 > 10, Tk < 70 High temp. heat pump

Classification according to the fluid distribution system

D1 - Electric or thermostatic expansion valve: a system that is little used in the industry, although which could have applications in liquid cooling units, heat pumps and commercial or small industrial installations (slaughterhouses).

D2 - Gravity: from LP cylinders supplied by a float expansion valve, the circulating output can be 6 to 8 times the vaporised output, the pressure is essentially the same as the evaporation pressure, the connecting lines have equivalent diameters. All of the following applications are generally located in buildings.

• Many small and medium-size coolers use finned type evaporators that are gravity fed by individual cylinders (fruit coolers, slaughterhouses).

• Freezing or cooling tunnel evaporators supplied by individual cylinders (yoghurt tunnels, fluidised beds, etc.).

• Evaporators immerged in tanks of iced water or brine supplied by overheating cylinder (dairies, ice cream manufacturers, etc.).

• Multiple-tube evaporators supplied by floater expansion valve (water coolers or glycol water for breweries, etc.).

22 Guide d'étude des risques technologiques, Technological risks study guide (AFF / Club Ammoniac - 1995).

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D3 - By low pressure pump: from a supply cylinder, the liquid of which is expanded by a HP or LP floater expansion valve, the liquid output from the pump is 4 to 10 times the vaporised output and the discharge pressure is 3 to 4 bar greater than the intake pressure. The connecting lines can be long, of large diameter, and are located within the buildings. Certain sections can circulate in the open air on a framework. The applications are increasingly numerous (freezing or cooling tunnel evaporators, freezer plate cabinets, large coolers).

Classification according to condensation mode

C1 - By air:

• Air-cooled refrigerant condenser: it is installed outside except in the case of heat pumps; the condenser and the subcooler are thus integrated in the process.

• Evaporative refrigerant condenser (exterior): the tank is generally located at the liquid outlet.

C2 - By water:

• Horizontal multipipe condenser (interior or exterior).

• Vertical trickling condenser (exterior).

Classification according to the number of compression stages

E1 - Single stage units: temperature difference (Tk - T0) less than 50°K.

E2 - Two-stage units: temperature difference (Tk - T0) greater than 50°K.

Classification by installation type (8 main applications)

The diagrams below indicate the habitual location of the installations, the nature and most frequent arrangement of the main equipment, the size range of pipes and the possible risk(s).

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A1 - Liquid cooler unit

This type of installation is very widely used in all agriculture & food industries and in the air-conditioning sector.

A2 - Ice skating rink

These installations form part of the rare installations where ammonia is used in a public facility. The pipe network maintaining the ice rink is embedded in a concrete slab and may extend several tens of km in length.

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A3 - Brine and iced water tanks

This type of installation is used in dairies and in air-conditioning facilities. The brine or iced water is an indirect cooling system.

A4 -Freezing rooms and tunnels

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A5 - Quick-frozen food storage

A6 - Cooling rooms

These installations are used in all agriculture & food industries.

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A7 - Freezing tunnels

These installations are used in all agriculture & food industries.

An 8th group, referred to as "A8", made up of high temperature air/air heat pumps is not depicted here.

The following table includes all of the installations mentioned above while associating the various classification criteria presented.

Application Evaporation Distribution Condensation Stages

A1 T2 or T3 D2 C1 or C2 1 or 2

A2 T3 D3 C1 1

A3 T3 D2 C1 or C2 1

A4 T3 D2 or D3 C1 1

A5 T2 D3 C1 2

A6 T3 D2 or D3 C1 1

A7 T1 D2 or D3 C1 2

A8 T4 D1 C2 1 or 2

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Administrative situation

Article 1 of the Act of July 19, 1976 requires facilities liable to compromise public safety and sanitation to request authorisation or declare their activities. Those concerned fall under the various headings of the list of classified industrial sites for the protection of the environment.

Refrigeration (or compression) installations operating at gauge pressures above 1 bar are thus concerned, particularly if they compress or use a flammable or toxic fluid such as liquefied ammonia.

Until July 1992, facilities were subject to either:

• authorisation, for input power greater than 300 kw (361.A.1), or

• declaration, for input power less than or equal to 300 kw (361.A.2).

Section 361 is essentially deals with sound nuisance possibly associated with the operation of the main equipment in facilities (ventilators, compressors, etc.) and not by the risks associated with the toxicity and the flammability of ammonia. In certain installations, large quantities of ammonia can be present, part of which is contained in a buffer tank with a capacity of several m3 (confined or otherwise).

This tank can be considered as a liquid ammonia storage facility, possibly associated with a refrigeration facility, and governed in this respect by section 50.

• under the authorisation regime, when the storage facility consists of tanks (or recipients) having a unitary capacity of:

- greater than 10 t or if the total quantity of the ammonia stocked exceeds 50 t (50.1),

- greater than 50 kg but less than or equal to 10 t, if the total quantity of ammonia stocked is greater than 150 kg but less than or equal to 50 t (50.2),

- less than or equal to 50 kg, if the total quantity of ammonia stocked is greater than 5 t but less than or equal to 500 t (50.3.a).

• under the declaration regime, when the storage facility consists of tanks or recipients with a unitary capacity less than or equal to 50 kg, if the total quantity of ammonia stocked is greater than 150 kg but less than or equal to 5 t (50.3.b).

With this interpretation of the nomenclature, the majority of refrigeration installations subject to declaration as per section 361 should have benefited from the authorisation regime. Dated February 20 and April 2, 1976, two documents from the SEI ("Service de l'Environnement Industriel", Service for the Industrial Environment) stipulate, respectively:

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• that "all refrigerated storage facilities having liquid ammonia storage greater than 50 kg, the quantity stocked being greater than 150 kg, fall within the 2^nd class of the classified installations nomenclature, independently of activities conducted jointly",

• that "an ammonia storage facility (cylinders, for example) must be properly distinguished which, owing to its size, may be classified as such, from ammonia tanks existing in the liquefied ammonia system of refrigeration equipment, which form an integral part of this installation classed in the 3rd category under the terms of section 361, and cannot be considered as a storage facility".

The Decree of July 7, 1992 modified the nomenclature by removing activity No. 50 and by creating section No. 1136 "Emploi ou stockage de l'ammoniac" (Use and storage of ammonia). All ambiguity has thus been removed, as the use and storage of liquefied ammonia is now governed by:

• an authorisation with public easement, if the total quantity likely to be present in the installation is greater than or equal to 500 t (1136.1),

• an authorisation, if the total quantity likely to be present in the installation is greater than 50 t, but less than 500 t (1136.2) or if the ammonia is stored in a single tank:

- greater than 50 kg, if the total quantity likely to be present in the installation is greater than 150 kg, but less than or equal to 50 t (1136.3),

- less than or equal to 50 kg, if the total quantity likely to be present in the installation is greater than 5 t, but less than or equal to 50 t (1136.4a),

• a declaration, if the ammonia is stored in tanks with a capacity less than or equal to 50 kg and if the total quantity likely to be present in the installation is greater than 150 kg, but less than or equal to 5 t (1136.4b).

Section 361 will be replace by section 2920 "Installations de réfrigération ou compression fonctionnant à des pressions effectives supérieures à 105 Pa", (Refrigeration or compression installations operating at gauge pressures above 105 Pa),

• compressing or using flammable or toxic fluids, the input power being greater than 300 kW (authorisation) or greater than 20 kW, but less than or equal to 300 kW (declaration),

• in all other cases, the input power being greater than 500 kW (authorisation) or greater than 50 kW, but less than or equal to 500 kW (declaration).

Nuisances and risks associated with the operation of installations

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A refrigeration installation, like all other technical equipment, poses specific risks.

These risks are especially related to the products used in the transfer loops to trap, transport and draw off excess calories.

Generally speaking, the heat transfer fluid may be flammable, toxic and liable to effect the ozone layer in the upper atmosphere or participate in the "greenhouse effect".

Nuisances

It should be reminded that refrigeration installations:

• generally operate in a closed system and generate few nuisances during normal operation,

• often are equipped with a cooling system using "evaporative" type refrigerant condensers possibly creating water vapour (steam) to a certain extent,

• do not produce waste, excluding any used oil,

• are equipped with potentially noisy equipment (compressor, associated cooling equipment, etc.) and must be designed or equipped to limit noise pollution as much as possible.

Potential risks

The main physical and thermodynamic characteristics of the ammonia used as a refrigerant and a Material Safety Data Sheet are presented in the appendices hereto²³. Fire / explosion risks

Ammonia is considered as a relatively non-flammable gas²⁴. Its explosive limits in air are between 15 and 28%. However, a study indicates that the L.E.L. may be reduced by 4% in presence for a cloud consisting of oil (simultaneous lubricant leak) and aerosol ammonia²⁵.

The self-ignition temperature of ammonia is 630°C. As it dissolves in nitrogen beginning at 450 - 550°C, the combustion obtained can result from the hydrogen formed.

23 Appendices 3 and 4: physical and thermodynamic characteristics of ammonia / Material Safety Data Sheet.

24 Material Safety Data Sheet No. 16 (I.N.R.S.)

25 A.F.F. Seminar / International Institute of Ammonia Refrigeration (U.S.A.).

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Although much greater than the majority of hydrocarbons, its minimal ignition energy (680 mJ) is nevertheless less than that delivered by a switch spark (1 J).

Ammonia's flammable and explosive character, particularly in a confined space, is a subject of controversy. A bibliography compiled in 1991 ²⁶ stipulates that all the flammability and explosivity characteristics published indicate that ammonia is a combustible gas which is quite less reactive, vis-à-vis air, than the majority of other combustible gas, and methane in particular. As such, the minimum ignition energy of an air / ammonia mixture is greater, the flame in the mixture propagates with more difficulty and slower; the violence of the explosion is weaker in a closed recipient. The study sites a few accidents abroad in which ignition/explosion of ammonia is suspected.

A summary of the accidents concerned is provided in the appendix hereto²⁷.

Given the current level of understanding and without precise elements about these accidents (no known case is recorded in France), this risk is touched upon only lightly in this study. The same is not true, however, for fires associated with the environment in the vicinity of the installation (numerous cases are known particularly as a result of the insulation materials used), the latter possibly being the cause of a possible domino effect.

Toxic hazard

With the exception of air, rarely used in these conditions, all refrigerants are potentially harmful to man when their concentration in the air reaches a certain level. Fatal accidents resulting from anoxia have even been encountered with C.F.C.s. However, ammonia is one of the refrigerants whose toxicity is a dominant characteristic. The explosion of a 22-ton tank of ammonia in Dakar, Senegal on March 24, 1992 (129 dead and more than 1,100 injured) reminds us that the toxicity of this product can also result in a "delayed effect" which is responsible for numerous deaths even weeks after an accident.

Normally confined in the recipients and pipes of a refrigeration system, ammonia can be released to the open air in an accidental situation, especially resulting from:

• normal operation of safety devices (valves, blow-out discs),

• operational failure (a poorly-controlled purge of a circuit, etc.),

26 Etude bibliographique - Caractéristiques d'inflammabilité et d'explosivité de l'ammoniac, Bibliographical study - Inflammability and explosivity characteristics of ammonia

(INERIS / Mr. PINEAU/ Mrs. ABIVEN/ Mr. CHAINEAUX - October 1991).

27 Appendix 7: list of known accidents since 1968 (France / World).

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• through a limited leak (seal, loss of seal on a valve, corrosion, etc.),

• after equipment rupture (explosion caused by a fire, impact or equipment failure, etc.).

The ammonia released may then form a toxic cloud in the atmosphere and possibly cause water pollution if a permanent flow of water is located nearby (wastewater/rainwater collector, etc.) or following inappropriate maintenance or servicing (sprayed water from a curtain not collected, etc.).

• A limited leak corresponds to a continuous liquid or gaseous phase release and at a constant or nearly constant rate. Its duration depends on the technical characteristics of the installation, the location of the "break", and the emergency response resources and the intervention time.

• The rupture instantly releases a significant quantity or all of the ammonia essentially in the form of an initial flash (up to 20% of the mass of NH3 released for an ambient temperature of 25°C), generally followed by a second release corresponding to the slow vaporisation of the residual liquid product released.

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ACCIDENT ANALYSIS

This study essentially concerns refrigeration installations using ammonia as refrigerant.

However, in order to better understand and to place the risks associated with these installations in perspective, quantified information has also been collected on numerous accidents, both French or foreign, in other industrial or agricultural activities and in the field of transport. The processing of these data allows a number of comparisons to be made using general indicators (geographic distribution, nature, accident causes and consequences, etc.).

Furthermore, while the nature and significance of the hazards presented are particularly different, the case studies bring into play liquid, gaseous ammonia or its aqueous solutions. These various phases can be presented for a given activity or during an accident (normal physical state of the product, transfer of risks or pollution during an intervention in a normal or accidental situation, etc.). Excluding special cases that are especially associated with the type and the consequences of certain accidents, the ammoniacal solutions used as liquid fertilizers are not taken into account however.

The sample studied consists of:

• 91 French refrigeration accidents (January 1980 to December 1994),

• 44 foreign refrigeration accidents (January 1958 to December 1992),

• 71 French accidents excluding refrigeration (August 1968 to December 1994),

• 150 foreign accidents excluding refrigeration (July 1959 to May 1994).

The first approach is then completed by a detailed presentation of a few representative and particularly significant accidents in terms of feedback (cause of the accident, sequence of events, consequences, etc.).

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Nature and characteristics of the sample studied

A biographical study and a query of the ARIA database enabled us to identify 356 accidents, from July 1959 to December 1994, involving ammonia and/or its aqueous solutions. The compiled sample is very diverse owing to the diversity of the sources of information, the kind and size of the events, as well as the more or less high level of detail of the information gathered.

The following table thus shows that 14% to 32% of the accidents studied generally lack information (origin of the toxic leaks, possible release of ammonia during a fire or following an explosion, consequences of the accident, etc.).

France (162) Abroad (194)

General information R²⁸ (91) not R²⁹ (71) TOT. R (44) not R (150) TOT.

Nb³⁰ % Nb % % Nb % Nb % % Few/no accidents reported 28 30.8 10 14.1 23.5 12 27.3 52 31.8 33.0 Fire /explosion (NH3 leak?) 23 25.3 1 1.4 14.8 2 4.6 9 6.0 5.7 Origin of leak not specified 13 14.3 8 11.3 13.0 15 34.1 39 26.0 27.8

Considering the various elements mentioned above, the use of this population for comparison purposes must be undertaken with care. The term "aggregate indicators" is thus used rather than "statistics". In order to ensure a minimum amount of consistency in the analysis presented below, the French and foreign accidents as well as the accidents concerned are systematically differentiated.

Consequently, the accidents studied are split according to the following 4 criteria:

• French / foreign / related or not related to a refrigeration installation.

A short presentation of the accidents in the field of refrigeration is enclosed at the end of this document³¹.

28 Refrigeration installations

29 Other installations (excluding refrigeration).

30 Number of known accidents.

31 Appendix 7: list of known refrigeration accidents since 1958 (France / World).

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Stakes and key figures

Of all the accidents studied, 54.5% occurred abroad and 45.5 % in France. Refrigeration installations represent 56.2% of the accidents in France and 22.7% of the accidents abroad.

The following tables present a distribution of the activities concerned, the typology of the accidents and their origins and consequences (an accident may correspond to several items).

Annual distribution

In this distribution of the accidents studied and the human consequences, the victims among the employees, rescue personnel and the public are not distinguished.

France (162 cases) Abroad (194 cases)

Year R (91 cases) not R (71 cases) R (44 cases) not R (150 cases)

A D I E/C A D I E/C A D I E/C A D I E/C

< 1980 - - - - 3 6 >27 ? 16 14 270 - 64 98 1800 >22300 1980/86 13 - 1 - 11 2 16 ? 9 14 166 >4100 48 30 >1400 >27000

1987 3 - 1 - 3 - - ? 3 12 50 200000 6 10 72 21000

1988 5 1 2 30 10 - 54 - 3 - - - 8 2 26 >1220

1989 7 - - >28 9 - 3 >900 5 1 1700 9100 12 11 680 >52400 1990 12 - 7 >600 9 - 12 ? - - - - 4 3 >400 >7000

1991 8 - 5 >35 4 - 1 22 2 - 6 - 4 17 150 >500

1992 12 - 7 ? 5 - 4 700 6 1 9 ? 2 129 1150 -

1993 10 - 42 ? 8 - 19 - - - - - 1 - 9 -

1994 21 - 122 >500 9 2 4 >20 - - - - 1 - ? - TOTAL 91 1 187 >1200 71 10 >140 >1700 44 42 >2200 >210000 150 300 >5600 >131000 A: number of accidents D: number of deaths I number of injured / intoxicated E/C: number of people evacuated / confined

The consequences of accidents abroad are generally more severe (victims, etc.) and are most often known as a result of widespread international coverage (notification, press, etc.).

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Of the population studied in France, refrigeration installations are responsible for 50 to 70% of known accidents and potentially involving ammonia or its aqueous solutions.

Undoubtedly, numerous other cases are not declared, particularly those that occur in small installations. A single accident resulted in the death of one person while there were 10 victims in accidents that were not refrigeration-related. This proportion (approx. 1/10) is appreciably less than that calculated based on foreign accidents (1/2).

The number of deaths/accident ratios are as follows:

Country Refrigeration related Not refrigeration related

France 0.01 0.14

Abroad 0.95 2.00

The people that were injured, effected or more or less intoxicated by the ammonia cloud are most generally employees or rescue personnel, and rarely the general public.

In France, confinement or evacuation is most often limited to the employees at the site where the accident occurred.

Monthly distribution of accidents according to the days of the week (French accidents)

The following two tables provide the distribution of French refrigeration-related accidents according to the month of the year and the days of the week. The foreign accidents that are excessively varied in space and time are not treated.

Month R (91 cases) not R

(71 cases) Day R (91

cases)

not R (71 cases)

Nb % Nb % Nb % Nb %

January 5 5.5 1 1.4 Monday 15 16.5 9 12.5 February 2 2.2 5 7.0 Tuesday 11 12.1 8 11.1 March 7 7.7 8 11.3 Wednesday 12 13.2 8 11.1 April 3 3.3 5 7.0 Thursday 19 20.9 17 23.6 May 3 3.3 6 8.5 Friday 18 19.8 13 18.1 June 11 12.1 11 15.5 Saturday 10 11.0 11 15.3 July 6 6.6 2 2.8 Sunday 6 6.6 5 6.9 August 17 18.7 5 7.0

September 13 14.3 7 9.9 October 12 13.2 10 14.1 November 7 7.7 3 4.2 December 5 5.5 8 11.3

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There are generally more accidents in June and during the months of August, September and October. The available information rarely indicates the exact circumstances, although the periods observed correspond to annual holiday periods (fewer people at work), seasonal operation stoppages (shut-down/restarting of installations) and large outdoor job sites (refurbishing of abandoned sites, etc...). The intensive use of equipment associated with hot summer temperatures may also be considered for the refrigeration installations.

In the sample studied, both refrigeration-related and non refrigeration-related accidents occur most often on Thursdays and Fridays. For the refrigeration-related accidents, the start of the week is also a sensitive period compared to other activities where numerous cases are recorded on Saturday (continuous production operations, etc...).

Regional distribution

The following table presents the region distribution (France) of the accidents studied.

Region Refrig. (91) Not refrig. (71) Total (162 cases)

Nb % Nb % Nb %

Alsace 5 5.5 3 4.2 8 4.9

Aquitaine 8 8.8 8 11.3 16 9.9

Auvergne 4 4.4 - - 4 2.5

Basse Normandie 6 6.6 1 1.4 7 4.3

Burgundy 3 3.3 5 7.0 8 4.9

Brittany 16 17.6 3 4.2 19 11.7

Centre - - 3 4.2 3 1.9

Champagne Ardenne 4 4.4 4 5.6 8 4.9 Franche Comté 1 1.1 1 1.4 2 1.2 Haute Normandie 1 1.1 5 7.0 6 3.7 Ile de France 1 1.1 3 4.2 4 2.5 Languedoc Roussillon 2 2.2 - - 2 1.2

Lorraine 10 11.0 3 4.2 13 8.0

Midi Pyrénées - - 1 1.4 1 0.6

Nord Pas de Calais 3 3.3 14 19.7 17 10.5 Pays de la Loire 8 8.8 2 2.8 10 6.2

Picardy 4 4.4 2 2.8 6 3.7

Poitou Charentes 1 1.1 - - 1 0.6 Provence Alpes Côte d'Azur 3 3.3 3 4.2 6 3.7 Rhône Alpes 11 12.1 10 14.1 21 13.0

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Five regions (Aquitaine, Brittany, Lorraine, Nord-Pas-de-Calais and Rhône-Alpes), each with between 8 and 13% of the accidents, concentrate 53% of the cases listed.

For the Aquitaine and Rhône-Alpes regions, the distribution between refrigeration- related activities and the other activities is balanced (50%). It can be noted, however, that:

• Brittany and its significant agriculture & food activity (animal husbandry, slaughterhouses, etc.) represent 18% of refrigeration-related accidents (4%

for the other installations),

• the Nord-Pas-de-Calais with its heavy industry especially associated with ammonia derivatives (fertilizer, etc.) represents 20% of non refrigeration- related accidents (3% for refrigeration installations),

• certain regions are particularly concerned by accidents related to the agricultural use of ammonia for soil management purposes (Champagne- Ardennes, etc.).

These regions are also ranked number one in terms of the overall capacity of their perishable foodstuff storage facilities, including Brittany with 2,357,107 m3 (production region), Rhône-Alpes with 1,430,940 m3 and Nord with 1,272,401 m3 (consumption regions). This is also true for Pays-de-la-Loire (1,211,100 m3) or Aquitaine (701,742 m3) which have a large volume of fruit packinghouses. Ile-de-France, however, with 1,684,735 m3, does not stand out in terms of the number of accidents³². Distribution by activity

The lack of homogeneity of the information collected must be mentioned again, especially concerning the foreign accidents. The databases generally mention only the most significant events; the kind of accident, its origin and the activity at issue are not always indicated. In addition, the sample studied only includes a limited number of accidents (356 cases).

Concerning the accidents and of the 745 ammonia-related incidents between 1977 and 1979, the "California Department of Industrial Relations, Division of Labour Statistics on Research" gives the following distribution³³:

• factories 28.2% • agriculture 11.1% • transports 3.5%

• misc. 18.5% • services 11.1% • construction 2.8%

• retailers 16.0% • wholesalers 8.6% • mining 0.1%

32 L'entreposage frigorifique français en chiffres, French cold storage in numbers - F. BILLIARD & G.

PIERSON - October 1992).

33 Eléments de sûreté chimique et de désastrologie, Elements of chemical safety and disasterology (C.E.A. / D.A.S. - M. ANDURAND - December 1989).

Current situation and perspectives

CONTENTS

GLOSSARY

INTRODUCTION

History

Current situation and perspectives

LIQUEFIED AMMONIA

REFRIGERATING INSTALLATIONS

Cold production

The use of cold and installation typology

Administrative situation

Nuisances and risks associated with the operation of installations

ACCIDENT ANALYSIS

Nature and characteristics of the sample studied

Stakes and key figures